warpig883
Moderator
Posts: 873
(10/24/01 7:46:50 am)
| Edit | Del Re: So, what do you think?
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I used to have a job where we measured things down to the ten thousanths of an inch .0001. If ya really want to mess up a smartass college kind sometime when your wrenching on something start asking for you wrench sizes in decimals. .437 for a 7/16 or .500 for a 1/2. Really rattles their brain from what I have seen. they can do it on paper but have a problem applying it.

The one that always get me chuckling is when measuring something with a tape measure and it comes out to one inch I will say its 10 tenths or 8 eights. people have no idea what in the hell I am talking about. Same way with 2/16ths for a 1/8th

Im' done now. Those are just some of the twisted little games I like to play with people when I am bored.
I am not happy unless I am miserable

NeoDebo
V.I.P. Forum Host
Posts: 281
(10/24/01 8:02:24 am)
| Edit | Del Group size...
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This is the way that I do it:

Measure the longest distance between the outside edges of the two holes that are furtherest apart. This distance will equal the diameter of a circle that will encompass all holes. I figure this to be my group size.

All holes may be completely encompassed by a circle of this diameter with at least two (perhaps more) holes each sharing a single point with the circle.

I measure this with a small pocket-size tape measure. Use calipers for better accuracy.

I usually just throw out the 'flyer' (if any), then measure the largest dimension of the cluster of holes, then subtract one caliber amount - viola! your group size.

If in the example / question posed above, the .277 measurement represents the measurement of the ragged hole from outer edge to outer edge at the widest point, then I have to agree with the first answer posted - .007 .

If the air temp is 80*F., then the speed of sound would be 1140.9667541557303 ft/sec = 778.9973333333334mi/hr.

If the air temp is 0*F., then the speed of sound would be 1052.0195392242635 ft/sec = 718.2684444444445 mi/hr.

What is shooting at you? If a 30-06 or some other centerfire rifle, probably not. A 45 cal 230gr ball, probably will. EDIT: On second thought, the 45 slug ans sound will be so close together, you probably receive them both at relatively the same time.

Question for you. If the bullet diameter of a .270 Winchester is .277, and the hole diameter is .277, where does the additional .007 come from?

The extra .007 would increase the size of the hole to .284, or would increase the bullet diameter to .284, thereby negating any possibility of having a "spread" of .277.

All 5 shots MUST pass through the exact same hole, or the "spread" would be greater than .277.

Answer has to be zero for measurement.
RuffItt

Edited by: ruffitt at: 10/25/01 12:56:59 am

ibtrukn
280freak
V.I.P. Member
Posts: 160
(10/23/01 1:22:53 pm)
| Edit | Del All So, what do you think?
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Got a quick quiz, going to see how many here know the correct method for measuring groups.

If you care to post a response, please limit it to a measurement only. No fair saying things that give clues to latecomers.

This is not a trick question, don't look for anything like that. I'm playing it straight. The worst you could say is that it IS extremely unlikely to the point of being probably impossible to attain in the real world, just meant as an exercise, nothing more.

A person shoots five shots at a target from a distance of 100 yards. He is shooting a gun chambered to .270 Win. When he goes to measure his group with a precision digital caliper, it shows an extreme spread of .277 inches. Using the standard formula for measuring groups, what would this one be? (Just looking for a measurement in tenths of an inch, not minute of angle or anything like that).

If you choose to post an answer, please make it your first choice and only post once. I'll post again tomorrow on this thread at about the same time as now to give most everybody a chance to try who wants to.

Different name
V.I.P. Forum Host
Posts: 340
(10/23/01 2:04:51 pm)
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ezSupporter
So, what do you think?
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WOW. 280Freak, I'm going to have to refer you to "gpostal" to comment of the digital measurements....
Measuring groups such as you present is beyond the boundaries of my realization...
Charlie D
Yesterday is history. Tomorrow, a
mystery. Today is a gift.

Flhunter
V.I.P. Forum Host
Posts: 636
(10/23/01 6:47:44 pm)
| Edit | Del Re: So, what do you think?
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There are two methods of measuring shot groups. The
first center to center of the two farthest apart shots
is used when all of the shots are not overlapping.

If you have a number of or all of the shots in the group
making a single hole you then determine the size of the
group by measuring the outermost edges of the hole and
then subtract the diameter of the bullet being used.

I'll agree with the answer of .007

ie: say you were using a 30-06 and you shot a one hole
group measuring 0.5" in diameter. You would subtract
the diameter of the bullet in thousands of an inch .308
from .500 and the group would be 0.192". In most cases
with the average rifle or pistol however, the groups are
large enough that none of the bullet holes are touching,
so you can measure center to center of the farthest
holes.

Never be afraid to try something new. Remember that amateurs built the ark. Professionals built the Titanic.

Flhunter
V.I.P. Forum Host
Posts: 637
(10/23/01 7:09:59 pm)
| Edit | Del Re: So, what do you think?
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My first answer is wrong !!!! I do not agree with .007 !!!! Can I have another try???? I know it !!!!! pick me...pick me....

Never be afraid to try something new. Remember that amateurs built the ark. Professionals built the Titanic.

Flhunter
V.I.P. Forum Host
Posts: 639
(10/23/01 7:47:33 pm)
| Edit | Del Re: So, what do you think?
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Dang it !!!! I knew that. 280 would not give me a second chance. I don't know what I was thinking....look at my example of a 30-06 it measures .308 there is the answer.
ARGH!!!!!!

Never be afraid to try something new. Remember that amateurs built the ark. Professionals built the Titanic.

warpig883
Moderator
Posts: 866
(10/23/01 8:32:31 pm)
| Edit | Del Re: So, what do you think?
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The way you posted it .2. The first digit is tenths then hundredths then thousanths. .007 is 7 thousanths of an inch. I spend hours at work reading vernier calipers and micrometers. Digital ones are for pansies. .27 is 27 hundreths and .277 is 277 thousanths.

For example half an inch .5 is five tenths .50 is 50 hundredths. and .500 is 500 thousanths all of these are the same thing as half an inch.
I am not happy unless I am miserable

On second thought, after going back and re-reading 280freaks post, I must say that I agree with you. His precise question required an answer expressed in 10ths of an inch, so .02 ((2/10)(20/100)(200/1000)) is the correct answer.
RuffItt

Edited by: ruffitt at: 10/23/01 10:21:10 pm

warpig883
Moderator
Posts: 868
(10/23/01 9:20:55 pm)
| Edit | Del Re: So, what do you think?
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I wasn't figuring the spread. I was just breaking down the measurment he gave. Just a little babbling on my part.
I am not happy unless I am miserable

I only referenced digital calipers for the perceived accuracy (whether they are actually any more accurate than a good quality vernier caliper is a subject for another day, perhaps), and the relative ease of getting a good and true measurement (if a fumble-fingered monkey like me can use one ... well). Nothing else was meant to have been implied.

Second, the bit about tenths of an inch also needn't be taken quite so literally. I mean, you certainly can if you want, you just don't particularly HAVE to! Please feel free to go to hundredths or thousandths if you want.

Now, back to the games; lots of good guesses with some solid reasoning shown. I'll give my answer and reasoning behind it tomorrow.

rayra
V.I.P. Member
Posts: 126
(10/23/01 10:34:29 pm)
| Edit | Del Re: So, what do you think?
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pish. as long as I can keep hitting a 12" steel plate at 400yds with a peep site, what do I care about thousandths?? ...grumble...stinkin' benchrest pansies..

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